I'm still in shock at this gratuitous act of electoral self-destruction, with all its national and international implications.
This Vox piece --- "5 winners and 4 losers from the 2016 election" --- succinctly hits on most of the main issues.
The things that terrify me the most about the forthcoming Trump regime are: (a) the further deterioration of the environment; (b) the destabilization of the international order (in part because of the emboldenment of Putin and the potential unravelling of NATO); (c) the entrenchment of a rightwing Supreme Court; (d) the likely end of the Affordable Care Act; (e) the erosion of other key social safety programs with a Ryan-authored budget (esp. Medicaid and food stamps); and (f) the emboldenment of racist, misogynistic, ableist, xenophobic, etc., discourse within American political culture.
On racism and xenophobia --- not just within the U.S. but throughout many other democratic societies -- this article, "White Riot," is a long and depressing read, but an excellent one. (The fact that Canada turns out to be the 'hero' of the story is cold comfort...)
One "what-could-have-prevented-this" comment: As my partner and most of my personal friends already know, I always thought that Bernie Sanders would've been a stronger candidate against Trump. This Daily Kos post nicely summarizes most of my reasons. (However, aside from a couple of posts on Facebook, I did not press this view because: (a) I was only about 70% confident in my judgement; and (b) I viewed Trump with such horror that I did not think it constructive to focus too much on the relative merits of Clinton versus Sanders.)
Finally, it looks like Clinton at least won the popular vote (the tally is 59,036,741 votes (47.6%) for Clinton versus 58,914,866 votes (47.5%) for Trump at the time of this post).
(Post updated at 6:22 with links and further thoughts.)